Embodiments of the present invention relate to charging and recharging a battery.
Batteries are used to store electrical charge, and can include many different compositions of an electrolyte between electrodes, such as an anode, cathode, and/or current collectors, which cooperate to store electrical charge and generate a voltage. Conventional large scale batteries are used to store energy to power automobiles, store solar or wind generated energy, or as power grid back up systems. Thin film batteries are used in applications that require a small battery with a high energy density such as, for example, portable electronics, medical devices and space systems. The battery component films of thin film batteries are thinner than conventional batteries, for example, the films can have thicknesses of less than 100 microns, providing batteries having thicknesses that are 100 times smaller than the thickness of conventional batteries. Thin film batteries can either be used individually, or multiple thin film batteries can be stacked together to provide more power or more energy.
Lithium batteries use lithium, such as lithium ion and (Li-ion) and lithium polymer (Li-polymer) batteries, and can have applications for conventional large scale batteries, as well as thin film batteries. It is desirable to minimize the time taken to recharge a conventional or thin film battery for almost any application, including mobile, electronic, or even automobile rechargeable batteries. However, a typical recharging process for lithium and other such batteries includes a first stage which uses a constant current charge level with a voltage limit set at a predefined value, for example, 4.2 volts. This stage takes about one hour, and the battery can be recharged to about 70% of the initial capacity. After the constant current recharge stage, in a second recharging stage, a constant voltage recharge step set to a voltage of 4.2 volts is used to charge the battery to full capacity in about two hours. Attempts have been made to charge lithium and other batteries at higher voltages than 4.2 volts to increase the rate of charging, but these methods have led to many negative effects, such as permanent damage to the cathode electrode material, plating of lithium metal on the anode electrode, or even reaction of liquid electrolyte with anode or cathode which can lead to fires or even small explosions. Thus, existing battery chargers for lithium and other batteries limit the maximum charging voltage to a predefined value, such as 4.2 volts, which increases charging time.
For reasons including these and other deficiencies, and despite the development of various recharging methods and apparatus for batteries, further improvements in recharging apparatus and methods are continuously being sought.